1. Field of the Invention
The present invention relates to a fastening fitting with a reinforcing member-tightening portion. More specifically, the invention relates to a fastening fitting with a reinforcing member-tightening portion adapted to be used for concrete-molding frames and the like.
2. Prior Art
A U-shaped fastening fitting (prior art) called U-clip shown in FIG. 6 has heretofore been widely used for the concrete-molding frames made of steel. This fastening fitting is convenient-for firmly supporting and fastening the required portions of the back surfaces of the molding frames, and is made of a rod of low carbon steel or medium carbon steel which is relatively cheaply available.
When a large concrete structure is to be constructed, in many cases, unit frames each having a unit weight of about 10 to 30 kilograms are used to be connected in many portions. In this case, the combined frames as a whole tend to lose the strength. In many cases, therefore, several to several tens of a pair of reinforcing members such as steel pipes are arranged in parallel cross on back surfaces of the frames.
The molding frames made of steel are generally assembled and secured together roughly in two ways depending upon the methods of tightening the molding frames and the reinforcing members. Here, however, the molding frame-fastening fitting and the fastening method are the same.
A first method is a widely employed method of executing the work according to which the surface plate of the molding frame is not perforated, and a plate-like separator is sandwiched by two pieces of molding frames by utilizing holes A perforated in the molding frames and is secured by the fittings penetrating therethrough. In this case, the reinforcing members are tightened by inserting a tightening fitting in a hole B separately perforated near the hole A in the frames. This method, however, has a demerit in that the reinforcing members are not tightened on a coaxial extension of the separator due to its structure.
According to a second method, holes C are formed in the surface plates of the molding frames, the ends of a rod-like separator are inserted in the holes C, C of the two surface plates, rod-like metallic fastening fittings are screwed into the threaded ends of the separator from the outer sides of the surface plates, thereby to fasten the reinforcing members. This method has a merit in that the reinforcing members can be tightened on a coaxial extension of the separator. However, since holes are formed in the surface plates, undesired ruggedness is formed after the concrete has been solidified, impairing smoothness on the finished surface and shortening the life (number of times of repetitive use) of the steel molding frames.
Besides, the conventional fastening fitting for steel molding frames requires a separate fitting for tightening the reinforcing members, involving difficulty in tightening to the reinforcing members. In particular, in high places and in narrow places where the scaffolding is not safe enough, three kinds of parts must be used, i.e., U-shaped fastening fitting, straight rod-like tightening fitting and tightening washer for securing the reinforcing members to the steel molding frames by using a separate tightening fitting, requiring laborious work for correctly positioning these parts and causing the work to become very difficult.
Besides, when a conventional fitting (metal tie) of the twisted type 201 (see FIG. 7) for tightening the reinforcing materials is inserted in the through holes of the frames 40, 40 that are vertically erected as shown in FIG. 8, one side which is longer tends to be lowered due to gravity, hindering the work.